The human food safety evaluation of new animal drugs

Drug residues

The use of veterinary drugs in animal production is necessary for the prevention and treatment of disease; however, such use may result in residues. Regulatory authorities administer legislative frameworks which ensure that foods derived from animals treated with approved veterinary drugs are safe for human consumption. A human food safety evaluation is conducted as follows: it estimates the risk to human health and safety--based on scientific assessment of the available information and data--formulates measures for controlling the risks identified, and communicates the findings and implications of the risk assessment to interested parties. Foods derived from animals are monitored for the presence of drug residues. The reported incidence of illegal residues from these programmes is very low. These findings reassure the public that veterinary drugs are effectively regulated and that food obtained from treated animals does not contain residues that might constitute a health hazard to consumers. Non-regulatory organizations, including the veterinary pharmaceutical industry, producer organisations, veterinarians and food processors, all contribute to a safe food supply. The food safety risk analysis framework is continually refined to ensure that the health of all consumers is protected.

Regulation of drugs used in feedlot diets

Diets fed to feedlot cattle typically contain nutritional ingredients along with other substances intended for various purposes, including growth promotion and disease prevention and control. Questions often arise as to the nature of those feed additives, whether and how they are regulated, and what is legal or illegal. In this article, the author discusses regulations pertinent to the use of drugs in feedlot diets. The article includes a discussion of what a drug is, how drugs are approved in the United States, what uses of drugs in feedlot diets are legal or illegal, and what is on the horizon for future drug regulations.

Residues of veterinary drugs at injection sites

Residues of veterinary drugs have potential implications for human food safety and international trade in animal-derived food commodities. A particular concern is the slow depletion of residues of some injectable formulations from the site of administration. Licensing authorities have adopted different approaches to the human food safety assessment of injection site residues. European agencies apply the maximum residue limit (MRL) for muscle to muscle at the injection site and specify a withdrawal period sufficient to ensure the ingestion of a 300 g portion of muscle, if comprised entirely of injection site tissue, does not exceed the acceptable daily intake. The agencies in Australia, Canada and the USA also exclude injection site residues from the MRL-setting process. These agencies evaluate the risk to consumers posed by potential acute manifestations resulting from the infrequent ingestion of injection site residues based on acute dietary exposure considerations. While all of these approaches protect the safety of consumers, the adoption of different approaches has potential implications for residue surveillance programs in the international trade in meat. In particular, when an exporting country establishes standards for residues at injection sites based on acute dietary exposure considerations and the importing country assesses these residues against the MRL for muscle, the unnecessary condemnation of meat and disruption to market access may result. The latter may represent a potential economical impost to the exporting country. An internationally harmonized approach to the risk analysis of residues of veterinary drugs at injection sites, which protects the safety of consumers and facilitates the international trade in meat, is needed.

Fish drug analysis--Phish-Pharm: a searchable database of pharmacokinetics data in fish

Information about drug residues and pharmacokinetic parameters in aquatic species is relatively sparse. In addition, it is difficult to rapidly compare data between studies due to differences in experimental conditions, such as water temperatures and salinity. To facilitate the study of aquatic species drug metabolism, we constructed a Fish Drug/Chemical Analysis Phish-Pharm (FDA-PP) database. This database consists of more than 400 articles that include data from 90 species (64 genera) of fish. Data fields include genus, species, water temperatures, the average animal weight, sample types analyzed, drug (or chemical) name, dosage, route of administration, metabolites identified, method of analysis, protein binding, clearance, volume of distribution in a central compartment (Vc) or volume of distribution at steady-state (Vd), and drug half-lives (t((1/2))). Additional fields list the citation, authors, title, and Internet links. The document will be periodically updated, and users are invited to submit additional data. Updates will be announced in future issues of The AAPS Journal. This database will be a valuable resource to investigators of drug metabolism in aquatic species as well as government and private organizations involved in the drug approval process for aquatic species.

Veterinary pharmacovigilance. Part 2. Veterinary pharmacovigilance in practice -- the operation of a spontaneous reporting scheme in a European Union country -- the UK, and schemes in other countries

Veterinary pharmacovigilance, as it operates in the European Union (EU), covers a very broad remit, including adverse effects in treated animals, exposed humans and the environment, and in addition, it extends to cover the violation of maximum residue limits. The mainstay of veterinary pharmacovigilance is the spontaneous reporting scheme working along side other systems such as those reporting on residues surveillance. One of the most well established schemes in the EU is that operating in the UK and this paper examines the evolution of that scheme and some of its findings, data from other countries, and information available from the literature. It also tentatively examines the ways that pharmacovigilance can be used for regulatory purposes, and the contribution from pharmacoepidemiology.

Approaches in the safety evaluations of veterinary antimicrobial agents in food to determine the effects on the human intestinal microflora

The administration of antimicrobial agents to livestock creates potential for antibiotic residues to enter the food supply and be consumed by humans. Therefore, as a process of food animal drug registration, national regulatory agencies and international committees evaluate data regarding the chemical, microbiologic, pharmacokinetic, pharmacodynamic, pharmacologic, toxicologic, and antimicrobial properties of veterinary drugs to assess the safety of ingested antimicrobial residues to consumers. Currently, European, Australian and United States guidelines for veterinary drug registration require a safety assessment of microbiologic hazards from consumption of antimicrobial residues taking into account the potentially adverse effects on human intestinal microflora. The main concerns addressed are selection of resistant bacteria in the gastrointestinal tract and disruption of the colonization barrier of the resident intestinal microflora. Current requirements differ among national agencies. Efforts are ongoing internationally to review and harmonize approaches and test methods and protocols for application to these microbiologic safety evaluations of antimicrobial drug residues in food. This review describes the background to current regulatory approaches used in applying in vitro and in vivo methods to set a microbiologic acceptable daily intake for residues in food derived from animals treated with an antimicrobial agent. This paper also examines the current research needs to support these evaluations.

Veterinary pharmacovigilance. Part 6. Predictability of adverse reactions in animals from laboratory toxicology studies

Toxicological studies are conducted on constituents of veterinary medicinal products for a number of reasons. Aside from being a requirement of legislation, they are carried out for predictive purposes in the assessment of user safety or for the determination of consumer safety, for example, in the elaboration of maximum residue limits or tolerances. Alternatively, the results of toxicology studies may be available as they have been generated for registration of the drug for human medicinal purposes. This paper examines if the results of such studies have any predictive value for adverse reactions, which might occur during clinical use in animals. A number of adverse reactions, notably the Type A (toxicology or pharmacology dependent) should be predictable from these laboratory studies. However, as with human pharmaceutical products, they have less utility in predicting Type-B reactions (idiosyncratic in nature).

Long-term Follow-up of Manipulative Treatment in a Horse with Back Problems

In order to objectively quantify the effect of manipulation on back-related locomotion anomalies in the horse, a recently developed kinematic measuring technique for the objective quantification of thoracolumbar motion in the horse was applied in a dressage horse that was suffering from a back problem. In this horse, clinically, a right-convex bending (scoliosis) from the 10th thoracic vertebra to the second lumbar vertebra was diagnosed. As a result, there was a marked asymmetric movement of the thoracolumbar spine. Functionally, there was severe loss of performance. Thoracolumbar motion was measured in terms of ventrodorsal flexion, lateral flexion, and axial rotation using an automated gait analysis system. Measurements were repeated before and 2 days after treatment, before the second treatment 3 weeks later, and at 4 weeks and 8 months after the second treatment to assess long-term effect. At the same time, performance of the horse was assessed subjectively by the trainer as well. Symmetry of movement improved dramatically after the first treatment. After this, there was a slight decrease in symmetry, but 8 months after the last treatment the symmetry indexes for the various joints were still considerably better than during the first (pre-treatment) measuring session. Subjectively, the trainer did not notice improvement until after measurement session 4. Between sessions 4 and 5 (at 4 weeks and 8 months after the second treatment) there was a change of trainer. The new trainer did not report any back problem, and succeeded in bringing the horse back to its former level in competition. It is concluded that manipulation had a measurable influence on the kinematics of the thoracolumbar spine. However, it is recognized that an improvement in symmetry of motion is not equivalent to clinical improvement and that other measures, such as changes in management, may be more decisive.

Animal drug human food safety toxicology and antimicrobial resistance--the square peg

This paper presents the traditional approach for the evaluation of human food safety used for animal drugs intended for food animals, and describes some of the difficulties posed by antimicrobial drug resistance. Like human drugs, animal drugs must be safe and effective for the patient. However, unlike human drugs, food derived from animals treated with the animal drug must also be shown to be safe for human consumption. The Food and Drug Administration has come to realize that antimicrobial drugs used in the treatment of the food animal have the potential to create a unique residue--increased numbers of microorganism that are resistant to antimicrobial drug treatment. The traditional toxicological paradigm for chemical residues does not apply to this unique microbiological residue. Information useful to a food safety evaluation may include the potential for the animal antimicrobial drug to diminish the susceptibility of microorganisms to human antimicrobial drugs, any human medical use of the drug, relationship to other human antimicrobial drugs, and the ability of the animal drug to alter the susceptibility of relevant microorganism to important human antimicrobial drugs. Yet to be developed are standardized approaches to quantify an acceptable level of resistant microorganism in food and to mitigate the hazard to assure that there is a reasonable certainty of no harm following the consumption of the edible food derived from the treated animal.

Interspecies considerations in the evaluation of human food safety for veterinary drugs

Residues are composed of the parent drug and metabolites, and therefore interspecies comparisons must involve a consideration of comparative xenobiotic metabolism. The focus of this article will be the residue studies that are required to establish human food safety, and the interspecies pharmacokinetic differences and similarities that impact drug residues in animal- derived foods. To illustrate the factors that can complicate and assist these comparisons, 2 drugs will be examined in detail: ivermectin and fenbendazole. In addition, the activities of 2 US programs, the Food Animal Residue Avoidance Databank (FARAD) and the NRSP-7 (National Research Support Project Number 7) Minor Use Animal Drug Program will be presented, along with strategies that may be employed in the study of species differences.

Impact of antimicrobial resistance on regulatory policies in veterinary medicine: status report

Increasing resistance to antimicrobial agents is of growing concern to public health officials worldwide. The concern includes infections acquired in hospitals, community infections acquired in outpatient care settings, and resistant foodborne disease associated with drug use in food-producing animals. In the United States, a significant source of antimicrobial-resistant foodborne infections in humans is the acquisition of resistant bacteria originating from animals. The US Food and Drug Administration's (FDA's) goal in resolving the public health impact arising from the use of antimicrobial drugs in food-producing animals is to ensure that significant human antimicrobial therapies are not compromised or lost while providing for the safe use of antimicrobials in food animals. The FDA's approach to the problem is multipronged and innovative. The strategy includes revision of the pre-approval safety assessment for new animal drug applications, use of risk assessment to determine the human health effect resulting from the use of antimicrobials in food animals, robust monitoring for changes in susceptibilities among foodborne pathogens to drugs that are important both in human and veterinary medicine, research, and risk management.